This invention relates to novel organic compounds and more particularly it relates to novel liquid crystal compounds useful as a components of liquid crystal materials.
As well known, liquid crystal compounds have been used for various display devices, making use of specific properties of the compounds in their liquid crystal phases such as dielectric anisotropy, refractive anisotropy, etc. These display devices refer to liquid crystal display elements using the electro-optic effect, thermo-optic effect or other optical effects of liquid crystals, along with advancements in electronics, a number of liquid crystal compounds have been used for liquid crystal display elements employing the field effects such as twisted nematic effect, guest-host effect, etc.
For these liquid crystal materials, however, there is no single substance which endures practical use with respect of its various characteristics such as mesomorphic range, operation voltage, response properties, etc.; thus it is the present status that practically, several kinds of liquid crystal compounds have been mixed together or the compounds have been mixed with several kinds of non-liquid crystal compounds to obtain materials which can endure practical use.
Recently a liquid crystal display element capable of being driven at low voltages has been required more and more, and in order to fulfill such a requirement, a liquid crystal composition having a large dielectric anisotropy value (hereinafter referred to as .DELTA..epsilon.) has been desired.
In general, in order to obtain such a liquid crystal composition having a large .DELTA..epsilon., a component having as large a .DELTA..epsilon. as possible may be used, but in this case it is necessary for the component to have a good compatibility with other components and also to broaden or at least not to narrow the mesomorphic range of the resulting composition.
Further, a liquid crystal composition having a large optical anisotropy value (.DELTA.n) can inhibit occurrence of color unevenness caused by partially non-uniform distance between the substrates of a liquid crystal display element and also can reduce the distance between the substrates; hence such a composition has an advantage that the field intensity of a cell using the composition can be enhanced even when the same voltage is impressed. Thus, a compound having a large .DELTA.n has been desired.